lib/: Add ispfchar(), and use it instead of its pattern

[alejandro-colomar]

• Queued after Add C-locale variants of isascii(3) APIs, and use them #1471.

---

Revisions:

v2

• Move ispfchar() under lib/string/.
• Document it in lib/string/README.

$ git rd 
1:  247466ab6 ! 1:  85d3d8cb4 lib/ctype/: ispfchar(): Add function
    @@ Metadata
     Author: Alejandro Colomar <alx@kernel.org>
     
      ## Commit message ##
    -    lib/ctype/: ispfchar(): Add function
    +    lib/string/ctype/isascii/: ispfchar(): Add function
     
         This function returns true if the input character is a character from
         the POSIX portable filename character set.
    @@ Commit message
     
      ## lib/Makefile.am ##
     @@ lib/Makefile.am: libshadow_la_SOURCES = \
    -   console.c \
    -   copydir.c \
    -   csrand.c \
    -+  ctype/ispfchar.c \
    -+  ctype/ispfchar.h \
    -   defines.h \
    -   encrypt.c \
    -   env.c \
    +   spawn.c \
    +   sssd.c \
    +   sssd.h \
    ++  string/ctype/isascii/ispfchar.c \
    ++  string/ctype/isascii/ispfchar.h \
    +   string/ctype/strchrisascii/strchriscntrl.c \
    +   string/ctype/strchrisascii/strchriscntrl.h \
    +   string/ctype/strisascii/strisdigit.c \
     
    - ## lib/ctype/ispfchar.c (new) ##
    + ## lib/string/README ##
    +@@ lib/string/README: Specific guidelines:
    + 
    + ctype/ - Character classification and conversion functions
    + 
    ++    isascii/
    ++  The functions defined under this directory
    ++  return true
    ++  is the character
    ++  belongs to the category specified in the function name.
    ++
    +     strchrisascii/
    +   The functions defined under this directory
    +   return true
    +
    + ## lib/string/ctype/isascii/ispfchar.c (new) ##
     @@
    -+// SPDX-FileCopyrightText: 2024, Alejandro Colomar <alx@kernel.org>
    ++// SPDX-FileCopyrightText: 2024-2025, Alejandro Colomar <alx@kernel.org>
     +// SPDX-License-Identifier: BSD-3-Clause
     +
     +
     +#include <config.h>
     +
    -+#include "ctype/ispfchar.h"
    ++#include "string/ctype/isascii/ispfchar.h"
     +
     +#include <stdbool.h>
     +
     +
     +extern inline bool ispfchar(unsigned char c);
     
    - ## lib/ctype/ispfchar.h (new) ##
    + ## lib/string/ctype/isascii/ispfchar.h (new) ##
     @@
    -+// SPDX-FileCopyrightText: 2024, Alejandro Colomar <alx@kernel.org>
    ++// SPDX-FileCopyrightText: 2024-2025, Alejandro Colomar <alx@kernel.org>
     +// SPDX-License-Identifier: BSD-3-Clause
     +
     +
    -+#ifndef SHADOW_INCLUDE_LIB_CTYPE_ISPFCHAR_H_
    -+#define SHADOW_INCLUDE_LIB_CTYPE_ISPFCHAR_H_
    ++#ifndef SHADOW_INCLUDE_LIB_STRING_CTYPE_ISASCII_ISPFCHAR_H_
    ++#define SHADOW_INCLUDE_LIB_STRING_CTYPE_ISASCII_ISPFCHAR_H_
     +
     +
     +#include <config.h>
2:  219955397 = 2:  1b917a73d lib/chkname.c: is_valid_name(): Use isalnum(3) instead of its pattern
3:  92332a203 = 3:  e2d77042a lib/chkname.c: is_valid_name(): Split Samba check
4:  1ead5c62f ! 4:  8fd9e48f6 lib/chkname.c: is_valid_name(): Use ispfchar() to simplify
    @@ lib/chkname.c
      
      #include "defines.h"
      #include "chkname.h"
    -+#include "ctype/ispfchar.h"
    ++#include "string/ctype/isascii/ispfchar.h"
      #include "string/ctype/strchrisascii/strchriscntrl.h"
      #include "string/ctype/strisascii/strisdigit.h"
      #include "string/strcmp/streq.h"

v2b

• tfix

$ git rd 
1:  85d3d8cb4 ! 1:  d339ea77e lib/string/ctype/isascii/: ispfchar(): Add function
    @@ lib/string/README: Specific guidelines:
     +    isascii/
     +  The functions defined under this directory
     +  return true
    -+  is the character
    ++  if the character
     +  belongs to the category specified in the function name.
     +
          strchrisascii/
2:  1b917a73d = 2:  7f83c18fe lib/chkname.c: is_valid_name(): Use isalnum(3) instead of its pattern
3:  e2d77042a = 3:  4c7cee7bc lib/chkname.c: is_valid_name(): Split Samba check
4:  8fd9e48f6 = 4:  d39008cae lib/chkname.c: is_valid_name(): Use ispfchar() to simplify

[stoeckmann]

The isalnum function is locale dependent. German umlauts are definitely not portable file characters, but will be as soon as setlocale is called.

[alejandro-colomar]

Thanks for the reminder!

I should use variants of these functions that work on the C locale exclusively.